OK, Now, I understand your reservations about Ideal! PBR who lays a white egg, must be real high in the leghorn genetics! No matter what you end up doing regarding breeding your own flock, it's guaranteed to be highly entertaining and educational. (IMO... but then, I lead a simple life!)
I think it's a combination of genetics and environment. If a chick starts out with optimal nutrition, she'll develop the reproductive system that will support production of a larger egg. (I've noticed that my hens eggs are larger after they've had a good protein feast.) Also, when she is...